I did do these back to back a couple years ago, but I used Walston and Dawnworld as the settings. For the most part I would use this to pick the worlds you use:
* High'n'dry needs a reason for the ship to be abandoned in the location it is in, which means low population, possibly a small, young world, and volcanic activity makes it a keeper.
* Death Station needs a location that is relatively underpopulated as well, and a reason to be doing shady experiments with combat drugs. I moved it to Dawnworld because of the peculiar impacts that world had on fertility, which was enough of a hook for weird effects on other hormones.
That said, consider Hradus as your starting world, where the crew gets their mission to seek out the High'n'Dry.
Scaladon is a good candidate for High'n'Dry because of the toxic oceans and the penchant of shooting people down who want to fly, which makes the final mission a little easy. People crowding ona plateau and afraid of the toxic ocean is a good setup for a rescue attempt as well.
For Death Station I'd consider Neon, low population, weird atmosphere, little to help a lab ship in orbit, but maybe a few different ways to get a hook to go visit it. It's also off the regular trade routes, so there wouldn't be a lot of traffic.